The following discussion of the prior art is intended to place the invention in an appropriate technical context and enable the associated advantages to be fully understood. However, any discussion of the prior art throughout the specification should not be considered as an admission that such art is widely known or forms part of the common general knowledge in the field.
It is known that the greater the air velocity from an air fan, the greater the noise generated. This generated noise can be a problem in confined areas, especially in areas shared by humans. This problem is no better exemplified than it is in a room ceiling fan where such noise is undesirable. To this end, it is known that the design of a ceiling fan has been limited by the amount of noise it generates relative to the amount of airflow and cooling effect provided.
Also, in the field of personal computers and peripheral devices such as printers and computer monitors, noise generated by the cooling fans can also be of concern to the users of these devices. At the same time, there is also a greater demand on such fans to displace the ever increasing heat generated.
Generally speaking, the more airflow a cooling fan can produce the better cooling effect created. The two basic ways of increasing the airflow of a fan is to increase the rotational speed of the fan rotor or increase the size of the fan rotor so that the blades move more air. However, the drawbacks of these methods are excessive power consumption and, as previously mentioned, noise. The same concerns can equally apply to other fluid movement devices such as axial flow pumps.
Various technologies have been developed in recent years for reducing noise generated by air and liquid movement devices. In Japanese Patent No. 10-197953 a fan noise separation system is taught including a grid member with a plurality of rectangular or circular openings located in an upstream air flow position proximate an air fan. In Japanese Patent No. 10-141294, a technique is disclosed for reducing noise using a barrier wall located within the blades of the impeller and which suppress the vortex flow. It is noted that in both these documents, a method of masking the noise only is presented and the cause of the noise is not addressed.
Accordingly, what is needed is a fan/rotor assembly that allows increased fluid flow without necessarily increasing the amount of noise generated. Ideally, it would also be desirable to increase the efficiency of the fan/rotor assembly.
It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.
It is an object of a preferred form of the present invention to provide a rotor coupling for a fluid displacement device such an air fan that reduces the noise generated by the fluid movement.